Portable electronic devices, such as mobile devices or wearable devices, rely on battery power to function. There are often more than one high power-consuming modules need to be on to perform a single task. For example, an activity monitoring device for pets allows the owner to capture content items for certain activities. It can involve high power-consuming modules, such as a camera, a high-speed processor and a WiFi interface. Therefore, there is a need to provide a smart power management system for the electronic devices, so that power consumption is minimized and battery life is optimized.